This invention relates to radar altimeters. More particularly, this invention relates to radar altimeters which measure height variations between adjacent parcels of terrain rather than from a reference datum plane. Still more particularly, this radar altimeter system relates to radars which employ digital methods for signal correlation, pulse summing, and peak pulse recognition.
A variety of phase modulated radars exist in the prior art, one of which is issued to Sol Rauch for a "Psuedo-Randomly Phased Modulated Radar Altimeter," U.S. Pat. No. 3,774,206, issued on Nov. 20, 1973. This particular reference is instructive for its teaching of the basics of the mechanics of phase modulation of radar signals and the benefits therefrom in addition to its general discussion of radar systems. However, this particular reference describes technology that is now at least 16 years old and does not incorporate the very significant advantages provided by the present system of predominantly digital operation, highly stable operation, and spread spectrum low power transmission and reception of signals.